Referring to FIG. 1, an existing swivel support device 1 includes a base seat 11, a first swivel arm 12 pivotally connected to the base seat 11, a second swivel arm 13 pivotally connected to the first swivel arm 12, and a mounting frame 14 pivotally connected to the second swivel arm 13. In assembly, the first swivel arm 12 has a projection portion projecting downward into the base seat 11, and is angularly adjustable to rotate with respect to the base seat 11. The second swivel arm 13 has a projection portion projecting downward into the first swivel arm 12 and is angularly adjustable to rotate with respect to the first swivel arm 12. The mounting frame 14 extends downward into the second swivel arm 13 and is angularly adjustable with respect to the second swivel arm 13. Accordingly, the mounting frame 14 can be conveniently adjusted to an appropriate position. However, during adjustment of the existing swivel support device 1, the mounting frame 14 is easily separated from the second swivel arm 13 by an accidentally applied upward external force. Likewise, because of the upward external force, the first and second swivel arms 12, 13 may be accidently separated from each other and the first swivel arm 12 may be accidently separated from the base seat 11.
Because the first and second swivel arms 12, 13 are rotatable 360 degrees, the range of adjustment is considerably wide. However, in practice, an installation space for the existing swivel support device 1 may be insufficient for such a wide adjustment range. In use, the existing swivel support device 1 can easily and accidentally over-rotate and impact a thing nearby. It is not easy to control the existing swivel support device 1.
On the other hand, when the mounting frame 14 is loaded with an object, an additional weight may influence the forces of rotating the first and second swivel arms 12, 13, and the mounting frame 14, and the joints formed thereamong require different rotation tightness. However, the existing swivel support device 1 is not adjustable to obtain desirable snugness for rotation of the joints.